The present invention relates to the field of signal processing and more particularly to tracking and eliminating of a discrete frequency noise signal from an information signal. Many physical systems contain discrete frequency noise components that corrupt the information signal. One example of this is the spin frequency noise and its harmonics which exist in gyroscopes. Other examples include the mechanical dithering of ring laser gyroscopes, discrete frequency acoustic noise, and vibrational noise in mechanical structures.
In the prior art, information signals contaminated with discrete frequency noise are typically sent through a conventional finite width notch filter to attenuate the information signal at the fundamental frequency component of the noise. Along with removing the information and noise at the fundamental frequency of the noise signal, a portion of the band adjacent to the noise frequency is also attenuated.
In prior art systems it is typical to be forced to tradeoff between notch filters with very narrow bandwidths, which retain as much of the information signal as possible and notch filters with broader bandwidths that remove wandering or jittering periodic noise signals but unduly attenuate the information signal and produce phase distortion at adjacent frequencies. Such tradeoffs are undesirable and limit the performance of signal processing systems. Furthermore, since conventional notch filters distort the phase of information signals and degrade fidelity, they are a poor choice for precision control and high resolution processing.
Accordingly, an object of this invention to provide an improved system and apparatus for attenuating a periodic noise component from an information signal.
Another object of the invention is to provide a signal processing system that generates a sinusoidal nulling signal for mechanically or electrically attenuating periodic noise components.
A further object of the invention is to provide a system and method for attenuating a periodic noise component by generating a nulling signal which has a phase, frequency and amplitude that substantially tracks the phase, frequency and amplitude of the noise component, while maintaining the information signal unperturbed except over a very narrow bandwidth.
Other objects of the invention will in part be apparent from the following description.